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Pierre Béland - One of the best experts on this subject based on the ideXlab platform.

  • organohalogen contaminants and metabolites in Beluga Whale delphinapterus leucas liver from two canadian populations
    Environmental Toxicology and Chemistry, 2006
    Co-Authors: Melissa A Mckinney, Daniel Martineau, Sylvain De Guise, Pierre Béland, Michel Lebeuf, Robert J Letcher
    Abstract:

    Contaminants described as organochlorines (OCs; e.g., polychlorinated biphenyls [PCBs]) are present in tissues of marine mammals, including Beluga Whales (Delphinapterus leucas), but the complexity of contaminant exposure often is not fully known. The PCBs, OC pesticides, polybrominated diphenyl ether (PBDE) flame retardants, methylsulfonyl (MeSO2)- and hydroxy (OH)-PCB metabolites, and OH-PBDEs and methoxylated (MeO)-PBDEs were determined in the liver of Beluga Whales from two Canadian populations: the St. Lawrence Estuary (SLB; n=6), and western Hudson Bay in the Canadian Arctic (CAB; n=11). The sigmaPCB, sigmaDDT, and sigmaPBDE concentrations were higher (p < 0.05) in SLB versus CAB. Of 18 detectable OH-PCBs in SLB (mainly 4-OH-CB107, 4-OH-CB112, and 4'-OH-CB120), only 4'-OH-CB120 was found in CAB. The sigmaOH-PCB concentrations were less than 0.2% of the sigmaPCBs in both populations but were higher (p < 0.05) in SLB (65 +/- 22 ng/g lipid wt) than in CAB (3.1 +/- 0.5 ng/g lipid wt). The sigmaMeSO2-PCB concentrations were higher in SLB (3801 +/- 1322 ng/g lipid wt) relative to CAB (77 +/- 23 ng/g lipid wt) and were 11 and 4%, respectively, of the sigmaPCB concentrations. Of the 15 OH-PBDEs, only two congeners were detectable, but not quantifiable (notably 2'-OH-BDE 68 and 6-OH-BDE 47), in animals from both populations. Of the 15 MeO-PBDEs, 4'-MeO-BDE 17 and 6-MeO-BDE 47 in the SLB (n=2) and 2'-MeO-BDE 68 and 6-MeO-BDE 47 in the CAB (n=2) had concentrations from 20 to 100 ng/g lipid weight. The OH-PBDEs and MeO-PBDEs most likely are of natural origin and accumulated in Beluga Whales, whereas the OH-PCBs and MeSO2-PCBs are metabolites derived from accumulated PCBs. Canadian Beluga Whale liver contains previously unidentified organohalogen contaminants and metabolites and, thus, a complexity of contaminant exposure that may be impacting the health of Canadian Beluga Whale populations.

  • biotransformation of polybrominated diphenyl ethers and polychlorinated biphenyls in Beluga Whale delphinapterus leucas and rat mammalian model using an in vitro hepatic microsomal assay
    Aquatic Toxicology, 2006
    Co-Authors: Melissa A Mckinney, Daniel Martineau, Sylvain De Guise, Pierre Béland, Augustine Arukwe, Robert J Letcher
    Abstract:

    Although polychlorinated biphenyls (PCBs) and polybrominated diphenyl ether (PBDE) flame retardants are important organic contaminants in the tissues of marine mammals, including those species from the Arctic, there is exceedingly little direct evidence on congener-specific biotransformation. We determined and compared the in vitro metabolism of environmentally relevant PCB (4,4'-di-CB15, 2,3',5-tri-CB26, 2,4,5-tri-CB31, 2,2',5,5'-tetra-CB52, 3,3',4,4'-tetra-CB77, 2,2',4,5,5'-penta-CB101, 2,3,3',4,4'-penta-CB105 and 2,3',4,4',5-penta-CB118), and PBDE (4,4'-di-BDE15, 2,4,4'-tri-BDE28, 2,2',4,4'-tetra-BDE47, 2,2',4,5'-tetra-BDE49, 2,2',4,4',5-penta-BDE99, 2,2',4,4',6-penta-BDE100, 2,2',4,4',5,5'-hexa-BDE153, 2,2',4,4',5,6'-hexa-BDE154 and 2,2',3,4,4',5',6-hepta-BDE183) congeners using hepatic microsomes of a Beluga Whale (Delphinapterus leucas) from the Arviat (western Hudson Bay) area of the Canadian Arctic. Ortho-meta bromine-unsubstituted BDE15, BDE28 and BDE47 were significantly metabolized (100%, 11% and 5% depleted, respectively) by Beluga, whereas control rat microsomes (from pooled male Wistar Han rats) metabolized BDE28, BDE49, BDE99 and BDE154 (13%, 44%, 11% and 17% depleted, respectively). CB15 and CB77 (putative CYP1A substrates) were more rapidly metabolized (100% and 93% depleted, respectively) by male Beluga than CB26 and CB31 (CYP1A/CYP2B-like) (25% and 29% depleted, respectively), which were more rapidly metabolized than CB52 (CYP2B-like) (13% depleted). Higher chlorinated CB101 and CB105 showed no depletion. Rat control microsomes metabolized CB15 to a lesser extent (32% depleted) than Beluga, but much more rapidly transformed CB52 (51% depleted, respectively). Within the 90 min in vitro assay time frame, the preference was towards metabolism of ortho-meta unsubstituted congeners (for both PCBs and PBDEs) in Beluga Whale, whereas for rat controls, meta-para unsubstituted congeners also substantially metabolized. For both Beluga Whale and rat, metabolic rates were inversely associated with the degree of halogenation. For the rapidly biotransformed CB15 and BDE15, water-soluble OH-metabolites were detected after incubation. These results indicate that CYP-mediated oxidative hepatic biotransformation is a metabolic pathway in the toxicokinetics of both PCB and PBDE congeners in Beluga Whales and in the rat model. This may suggest that the formation of potentially toxic oxidative PCB and PBDE products (metabolites), in addition to the parent pollutants, may be contributing to contaminant-related stress effects on the health of Beluga Whale.

  • methylsulfone polychlorinated biphenyl and 2 2 bis chlorophenyl 1 1 dichloroethylene metabolites in Beluga Whale delphinapterus leucas from the st lawrence river estuary and western hudson bay canada
    Environmental Toxicology and Chemistry, 2000
    Co-Authors: Robert J Letcher, Derek C G Muir, Krystyna Koczanski, Ross J Norstrom, Courtney D Sandau, Robert Michaud, Sylvian De Guise, Pierre Béland
    Abstract:

    Kowledge is limited regarding methylsulfone (MeSO2)-polychlorinated biphenyl (PCB), and especially MeSO2–2,2-bis(chlorophenyl)-1,1-dichloroethylene (DDE), metabolites in cetacean species. We hypothesized that the ability of Beluga Whale (Delphinapterus leucas) to biotransform PCB and DDE compounds, and to form and degrade their MeSO2 PCB and -DDE metabolites, is related to the capacity for xenobiotic metabolism. Adipose biopsies were collected from male and female Beluga Whale from distinct populations in the St. Lawrence River estuary (STL) and western Hudson Bay (WHB), Canada, which are contrasted by the exposure to different levels of cytochrome P450 enzyme-inducing, chlorinated hydrocarbon contaminants. The PCBs, DDTs, DDEs, 28 MeSO2 metabolites of 14 meta-para chlorine-unsubstituted PCBs, and four MeSO2 metabolites of 4,4′- and 2,4′-DDE were determined. The mean concentrations of total (Σ-) MeSO2-PCB in male STL Beluga (230 ng/g), and ratios of Σ-MeSO2-PCB to Σ-PCB (0.05) and Σ-precursor-PCB (0.17) were approximately twofold higher, whereas the Σ-precursor-PCB to Σ-PCB ratio was approximately twofold lower, than in male WHB Beluga. Both populations had a low formation capacity for MeSO2-PCBs with ≥six chlorines (<4% of Σ-MeSO2-PCBs). The congener patterns were dominated by trichloro- and tetrachloro-MeSO2-PCBs, and tetrachloro- and pentachloro-MeSO2-PCBs in WHB and STL animals, respectively. In addition to 2- and 3-MeSO2-4,4′-DDE, two unknown MeSO2-2,4′-DDEs were detected. The mean 3-MeSO2-4,4′-DDE concentration in STL Beluga (1.2 ng/g) was much greater than in WHB (<0.01 ng/g) animals. The concentrations of 4,4′-DDE, and not 3-MeSO2-4,4′-DDE, increased with age in male STL animals. We demonstrated that sulfone formation and clearance is related to metabolic capacity, and thus PCB, DDE, and MeSO2-PCB and -DDE toxicokinetics differ for STL and WHB Beluga. In the past, the capacity of odontocetes for PCB and DDE biotransformation leading to persistent sulfone metabolites has been underestimated. More information is needed for other cetacean species and marine mammals. The results of this study indicate that MeSO2-PCBs and -DDEs need to be included in the toxicologic risk assessment of PCB and DDT exposure in odontocetes, and perhaps for cetaceans in general.

  • a modelling based perspective on the past present and future polychlorinated biphenyl contamination of the st lawrence Beluga Whale delphinapterus leucas population
    Canadian Journal of Fisheries and Aquatic Sciences, 2000
    Co-Authors: Brendan E Hickie, Pierre Béland, Michael C S Kingsley, Peter V Hodson, Derek C G Muir, Donald Mackay
    Abstract:

    Individual- and population-based models are presented that provide quantitative assessments of the accumulation of persistent organic pollutants over the lifetime of the Beluga Whale (Delphinapteru...

  • effects of in vitro exposure of Beluga Whale leukocytes to selected organochlorines
    Journal of Toxicology and Environmental Health, 1998
    Co-Authors: S De Guise, Daniel Martineau, Pierre Béland, Michel Fournier
    Abstract:

    The effects of in vitro exposure to different organochlorines were evaluated on immune functions of Beluga Whale peripheral blood leukocytes and splenocytes. The effects of different concentrations of four different congeners of PCBs (138, 153, 180, and 169) as well as two DDT metabolites (p,p'-DDT and p,p'-DDE) were evaluated on phagocytosis and cell proliferation. The effects of dioxins and mixtures of organochlorines were also evaluated on cell proliferation. The different compounds tested had no marked effect on phagocytosis. PCB 138 and p,p'-DDT, but not PCB 153, PCB 180, PCB 169, and p,p'-DDE, reduced significantly the proliferative response of Beluga splenocytes cultured either with or without phytohemagglutinin A (PHA). Proliferation of Beluga splenocytes was not markedly affected by exposure to 5 ppm of PCB 138, 153, 180, and 169 separately. Exposure to a mixture of congeners 138, 153, and 180 (5 ppm each) significantly reduced splenocytes proliferation, but not the mixture of congeners 138, 153, 180, and 169 (5 ppm each). TCDD did not affect cell proliferation in our study. The reduced proliferation of Beluga cells exposed in vitro to mixtures of organochlorines at concentrations in the range of those observed in tissues of St. Lawrence Belugas might provide a basis to support the hypothesis that contaminants induce immunosuppression in these animals.

Robert J Letcher - One of the best experts on this subject based on the ideXlab platform.

  • comparative hepatic in vitro depletion and metabolite formation of major perfluorooctane sulfonate precursors in arctic polar bear Beluga Whale and ringed seal
    Chemosphere, 2014
    Co-Authors: Robert J Letcher, Melissa A Mckinney, Shaogang Chu, Gregg T Tomy, Christian Sonne, Rune Dietz
    Abstract:

    Perfluorooctane sulfonate (PFOS) has been reported to be among the most concentrated persistent organic pollutants in Arctic marine wildlife. The present study examined the in vitro depletion of major PFOS precursors, N-ethyl-perfluorooctane sulfonamide (N-EtFOSA) and perfluorooctane sulfonamide (FOSA), as well as metabolite formation using an assay based on enzymatically viable liver microsomes for three top Arctic marine mammalian predators, polar bear (Ursus maritimus), Beluga Whale (Delphinapterus leucas), and ringed seal (Pusa hispida), and in laboratory rat (Rattus rattus) serving as a general mammalian model and positive control. Rat assays showed that N-EtFOSA (38 nM or 150 ng mL(-1)) to FOSA metabolism was >90% complete after 10 min, and at a rate of 23 pmol min(-1) mg(-1) protein. Examining all species in a full 90 min incubation assay, there was >95% N-EtFOSA depletion for the rat active control and polar bear microsomes, ∼65% for ringed seals, and negligible depletion of N-EtFOSA for Beluga Whale. Concomitantly, the corresponding in vitro formation of FOSA from N-EtFOSA was also quantitatively rat≈polar bear>ringed seal>>>Beluga Whale. A lack of enzymatic ability and/or a rate too slow to be detected likely explains the lack of N-EtFOSA to FOSA transformation for Beluga Whale. In the same assays, the depletion of the FOSA metabolite was insignificant (p>0.01) and with no concomitant formation of PFOS metabolite. This suggests that, in part, a source of FOSA is the biotransformation of accumulated N-EtFOSA in free-ranging Arctic ringed seal and polar bear.

  • organohalogen contaminants and metabolites in Beluga Whale delphinapterus leucas liver from two canadian populations
    Environmental Toxicology and Chemistry, 2006
    Co-Authors: Melissa A Mckinney, Daniel Martineau, Sylvain De Guise, Pierre Béland, Michel Lebeuf, Robert J Letcher
    Abstract:

    Contaminants described as organochlorines (OCs; e.g., polychlorinated biphenyls [PCBs]) are present in tissues of marine mammals, including Beluga Whales (Delphinapterus leucas), but the complexity of contaminant exposure often is not fully known. The PCBs, OC pesticides, polybrominated diphenyl ether (PBDE) flame retardants, methylsulfonyl (MeSO2)- and hydroxy (OH)-PCB metabolites, and OH-PBDEs and methoxylated (MeO)-PBDEs were determined in the liver of Beluga Whales from two Canadian populations: the St. Lawrence Estuary (SLB; n=6), and western Hudson Bay in the Canadian Arctic (CAB; n=11). The sigmaPCB, sigmaDDT, and sigmaPBDE concentrations were higher (p < 0.05) in SLB versus CAB. Of 18 detectable OH-PCBs in SLB (mainly 4-OH-CB107, 4-OH-CB112, and 4'-OH-CB120), only 4'-OH-CB120 was found in CAB. The sigmaOH-PCB concentrations were less than 0.2% of the sigmaPCBs in both populations but were higher (p < 0.05) in SLB (65 +/- 22 ng/g lipid wt) than in CAB (3.1 +/- 0.5 ng/g lipid wt). The sigmaMeSO2-PCB concentrations were higher in SLB (3801 +/- 1322 ng/g lipid wt) relative to CAB (77 +/- 23 ng/g lipid wt) and were 11 and 4%, respectively, of the sigmaPCB concentrations. Of the 15 OH-PBDEs, only two congeners were detectable, but not quantifiable (notably 2'-OH-BDE 68 and 6-OH-BDE 47), in animals from both populations. Of the 15 MeO-PBDEs, 4'-MeO-BDE 17 and 6-MeO-BDE 47 in the SLB (n=2) and 2'-MeO-BDE 68 and 6-MeO-BDE 47 in the CAB (n=2) had concentrations from 20 to 100 ng/g lipid weight. The OH-PBDEs and MeO-PBDEs most likely are of natural origin and accumulated in Beluga Whales, whereas the OH-PCBs and MeSO2-PCBs are metabolites derived from accumulated PCBs. Canadian Beluga Whale liver contains previously unidentified organohalogen contaminants and metabolites and, thus, a complexity of contaminant exposure that may be impacting the health of Canadian Beluga Whale populations.

  • biotransformation of polybrominated diphenyl ethers and polychlorinated biphenyls in Beluga Whale delphinapterus leucas and rat mammalian model using an in vitro hepatic microsomal assay
    Aquatic Toxicology, 2006
    Co-Authors: Melissa A Mckinney, Daniel Martineau, Sylvain De Guise, Pierre Béland, Augustine Arukwe, Robert J Letcher
    Abstract:

    Although polychlorinated biphenyls (PCBs) and polybrominated diphenyl ether (PBDE) flame retardants are important organic contaminants in the tissues of marine mammals, including those species from the Arctic, there is exceedingly little direct evidence on congener-specific biotransformation. We determined and compared the in vitro metabolism of environmentally relevant PCB (4,4'-di-CB15, 2,3',5-tri-CB26, 2,4,5-tri-CB31, 2,2',5,5'-tetra-CB52, 3,3',4,4'-tetra-CB77, 2,2',4,5,5'-penta-CB101, 2,3,3',4,4'-penta-CB105 and 2,3',4,4',5-penta-CB118), and PBDE (4,4'-di-BDE15, 2,4,4'-tri-BDE28, 2,2',4,4'-tetra-BDE47, 2,2',4,5'-tetra-BDE49, 2,2',4,4',5-penta-BDE99, 2,2',4,4',6-penta-BDE100, 2,2',4,4',5,5'-hexa-BDE153, 2,2',4,4',5,6'-hexa-BDE154 and 2,2',3,4,4',5',6-hepta-BDE183) congeners using hepatic microsomes of a Beluga Whale (Delphinapterus leucas) from the Arviat (western Hudson Bay) area of the Canadian Arctic. Ortho-meta bromine-unsubstituted BDE15, BDE28 and BDE47 were significantly metabolized (100%, 11% and 5% depleted, respectively) by Beluga, whereas control rat microsomes (from pooled male Wistar Han rats) metabolized BDE28, BDE49, BDE99 and BDE154 (13%, 44%, 11% and 17% depleted, respectively). CB15 and CB77 (putative CYP1A substrates) were more rapidly metabolized (100% and 93% depleted, respectively) by male Beluga than CB26 and CB31 (CYP1A/CYP2B-like) (25% and 29% depleted, respectively), which were more rapidly metabolized than CB52 (CYP2B-like) (13% depleted). Higher chlorinated CB101 and CB105 showed no depletion. Rat control microsomes metabolized CB15 to a lesser extent (32% depleted) than Beluga, but much more rapidly transformed CB52 (51% depleted, respectively). Within the 90 min in vitro assay time frame, the preference was towards metabolism of ortho-meta unsubstituted congeners (for both PCBs and PBDEs) in Beluga Whale, whereas for rat controls, meta-para unsubstituted congeners also substantially metabolized. For both Beluga Whale and rat, metabolic rates were inversely associated with the degree of halogenation. For the rapidly biotransformed CB15 and BDE15, water-soluble OH-metabolites were detected after incubation. These results indicate that CYP-mediated oxidative hepatic biotransformation is a metabolic pathway in the toxicokinetics of both PCB and PBDE congeners in Beluga Whales and in the rat model. This may suggest that the formation of potentially toxic oxidative PCB and PBDE products (metabolites), in addition to the parent pollutants, may be contributing to contaminant-related stress effects on the health of Beluga Whale.

  • methylsulfone polychlorinated biphenyl and 2 2 bis chlorophenyl 1 1 dichloroethylene metabolites in Beluga Whale delphinapterus leucas from the st lawrence river estuary and western hudson bay canada
    Environmental Toxicology and Chemistry, 2000
    Co-Authors: Robert J Letcher, Derek C G Muir, Krystyna Koczanski, Ross J Norstrom, Courtney D Sandau, Robert Michaud, Sylvian De Guise, Pierre Béland
    Abstract:

    Kowledge is limited regarding methylsulfone (MeSO2)-polychlorinated biphenyl (PCB), and especially MeSO2–2,2-bis(chlorophenyl)-1,1-dichloroethylene (DDE), metabolites in cetacean species. We hypothesized that the ability of Beluga Whale (Delphinapterus leucas) to biotransform PCB and DDE compounds, and to form and degrade their MeSO2 PCB and -DDE metabolites, is related to the capacity for xenobiotic metabolism. Adipose biopsies were collected from male and female Beluga Whale from distinct populations in the St. Lawrence River estuary (STL) and western Hudson Bay (WHB), Canada, which are contrasted by the exposure to different levels of cytochrome P450 enzyme-inducing, chlorinated hydrocarbon contaminants. The PCBs, DDTs, DDEs, 28 MeSO2 metabolites of 14 meta-para chlorine-unsubstituted PCBs, and four MeSO2 metabolites of 4,4′- and 2,4′-DDE were determined. The mean concentrations of total (Σ-) MeSO2-PCB in male STL Beluga (230 ng/g), and ratios of Σ-MeSO2-PCB to Σ-PCB (0.05) and Σ-precursor-PCB (0.17) were approximately twofold higher, whereas the Σ-precursor-PCB to Σ-PCB ratio was approximately twofold lower, than in male WHB Beluga. Both populations had a low formation capacity for MeSO2-PCBs with ≥six chlorines (<4% of Σ-MeSO2-PCBs). The congener patterns were dominated by trichloro- and tetrachloro-MeSO2-PCBs, and tetrachloro- and pentachloro-MeSO2-PCBs in WHB and STL animals, respectively. In addition to 2- and 3-MeSO2-4,4′-DDE, two unknown MeSO2-2,4′-DDEs were detected. The mean 3-MeSO2-4,4′-DDE concentration in STL Beluga (1.2 ng/g) was much greater than in WHB (<0.01 ng/g) animals. The concentrations of 4,4′-DDE, and not 3-MeSO2-4,4′-DDE, increased with age in male STL animals. We demonstrated that sulfone formation and clearance is related to metabolic capacity, and thus PCB, DDE, and MeSO2-PCB and -DDE toxicokinetics differ for STL and WHB Beluga. In the past, the capacity of odontocetes for PCB and DDE biotransformation leading to persistent sulfone metabolites has been underestimated. More information is needed for other cetacean species and marine mammals. The results of this study indicate that MeSO2-PCBs and -DDEs need to be included in the toxicologic risk assessment of PCB and DDT exposure in odontocetes, and perhaps for cetaceans in general.

Alexander Ya. Supin - One of the best experts on this subject based on the ideXlab platform.

  • adaptation in the auditory system of a Beluga Whale effect of adapting sound parameters
    Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2019
    Co-Authors: V V Popov, Alexander Ya. Supin, Dmitri I Nechaev, Evgeniya Sysueva
    Abstract:

    The effects of adapting sounds (pip trains or pure tones) on auditory evoked potentials (the rate following response, RFR) were investigated in a Beluga Whale. During RFR acquisition, adapting signals lasting 128 ms each were alternated with test signals lasting 16 ms each; the test signal levels varied randomly. Adapting signals were trains of cosine-enveloped tone pips or pure tones. Pip rate varied with the envelope cosine cycle maintained at 0.125 of pip intervals and the cosine rise-fall time maintained at 0.0625 of pip intervals. Adapting signals shifted the amplitude-level function upward compared to the baseline (no adapting signal) function. The higher the adapting signal level was, the bigger the shift in the amplitude-level function was. The slower the pips were in the adapting signal, the smaller the adaptation effect was. A train of pips with a 0.0625-ms rise-fall time and 125 dB SPL shifted the function by 35-40 dB, whereas a train of pips with a 1-ms rise-fall time or a pure tone with the same SPL shifted the function by approximately 15 dB. The difference between the "fast" and "slow" adapting signals is supposed to be associated with their abilities to stimulate the auditory system in odontocetes.

  • differential hearing sensitivity in the adaptive background in a Beluga Whale
    Journal of the Acoustical Society of America, 2018
    Co-Authors: V Popov, Alexander Ya. Supin, Dmitry I. Nechaev, Evgeniya Sysueva
    Abstract:

    The ability of the auditory system to maintain high differential sensitivity in the adaptive background was investigated in a Beluga Whale (Delphinapterus leucas). Adaptive background was a train of tone pips following one another at a rate of 1 kHz. Each pip consisted of eight carrier cycles of 64 kHz. Every 128 ms, the train of pips was interrupted for 16 ms and replaced with a test signal (16-ms series of the same tone pips as in the adaptive background, but of another level). The level of the test signals varied from -15 to + 20 dB relative the level of adaptive background. Evoked potentials (the rate following response, RFR) produced by the test signals were recorded. Increasing of adaptive level led to RFR thresholds growth. The 10-dB rising of adaptive signals intensity level led to 7.8 dB rising of test signal threshold. The response amplitude dependence on the test stimulus level was almost independent of the level of the adaptive background. Thus, the Beluga’s auditory system displayed high sensitivity to the change in acoustic signal level in the high-level background. [This study was supported by the Russian Foundation for Basic Research (Grant No. 18-04-00088).]The ability of the auditory system to maintain high differential sensitivity in the adaptive background was investigated in a Beluga Whale (Delphinapterus leucas). Adaptive background was a train of tone pips following one another at a rate of 1 kHz. Each pip consisted of eight carrier cycles of 64 kHz. Every 128 ms, the train of pips was interrupted for 16 ms and replaced with a test signal (16-ms series of the same tone pips as in the adaptive background, but of another level). The level of the test signals varied from -15 to + 20 dB relative the level of adaptive background. Evoked potentials (the rate following response, RFR) produced by the test signals were recorded. Increasing of adaptive level led to RFR thresholds growth. The 10-dB rising of adaptive signals intensity level led to 7.8 dB rising of test signal threshold. The response amplitude dependence on the test stimulus level was almost independent of the level of the adaptive background. Thus, the Beluga’s auditory system displayed high sens...

  • adaptation processes in the auditory system of a Beluga Whale delphinapterus leucas
    PLOS ONE, 2018
    Co-Authors: V V Popov, Alexander Ya. Supin, Dmitry I. Nechaev, Evgeniya Sysueva
    Abstract:

    The effects of prolonged sound stimuli (tone pip trains) on evoked potentials (the rate following response, RFR) were investigated in a Beluga Whale. The stimuli (rhythmic tone pips) were of 64 kHz frequency at levels from 80 to 140 dB re 1 μPa. During stimulation, every 1000 ms stimulus level either was kept constant (the steady-state stimulation) or changed up/down by 20 or 40 dB. With such stimulus presentation manner, RFR amplitude varied as follows. (i) After a stimulus level increase, the response amplitude increased quickly and then decayed slowly. The more the level increased, the higher the response amplitude increased. (ii) After a stimulus level decrease, the response amplitude was suppressed and then recovered slowly. The more the level decreased, the stronger was the response suppression. (iii) At the end of the 1000 ms window, the response amplitude approached, but did not reach, the amplitude characteristic of the steady-state stimulation. As a result, both after a sound level increase and decrease, the responses were almost stabilized during an analysis time as short as 1 s. This stabilization is attributed to an adaptation process. RFR decay after initial increase could be approximated by an exponent with a time constant of 59.4 ±1.8 (standard error) ms; RFR recovery after initial decrease could be approximated by an exponent with a time constant of 139.2 ±9.9 ms.

  • influence of fatiguing noise on auditory evoked responses to stimuli of various levels in a Beluga Whale delphinapterus leucas
    Journal of the Acoustical Society of America, 2017
    Co-Authors: V Popov, Dmitry I. Nechaev, Evgeniya Sysueva, Alexander Ya. Supin
    Abstract:

    The post-exposure effect of fatiguing noise (half-octave band-limited noise centered at 32 kHz) on the evoked responses to test stimuli (rhythmic pip trains with a 45-kHz center frequency) at various levels (from threshold to 60 dB above threshold) was investigated in a Beluga Whale Delphinapterus leucas. For baseline (pre-exposure) responses, the magnitude-vs-level function featured a segment of steep magnitude dependence on level that was followed by a segment of little dependence (plateau). Post-exposure, the function shifted upward along the level scale. Due to the plateau in the magnitude-vs-level function, post-exposure suppression of responses depended on the stimulus level such that higher levels corresponded to less suppression. The experimental data may be modeled based on the compressive non-linearity of the cochlea. According to the model, post-exposure responses of the cochlea to high-level stimuli are minimally suppressed compared to the pre-exposure responses, despite a substantially increa...

  • auditory sensitivity to local stimulation of the head surface in a Beluga Whale delphinapterus leucas
    Journal of the Acoustical Society of America, 2016
    Co-Authors: V V Popov, Dmitry I. Nechaev, Alena Lemazina, Evgeniya Sysueva, Alexander Ya. Supin
    Abstract:

    Using the auditory evoked response technique, sensitivity to local acoustic stimulation of the ventro-lateral head surface was investigated in a Beluga Whale (Delphinapterus leucas). The stimuli were tone pip trains of carrier frequencies ranging from 16 to 128 kHz with a pip rate of 1 kHz. For higher frequencies (90–128 kHz), the low-threshold point was located next to the medial side of the middle portion of the lower jaw. For middle (32–64 kHz) and lower (16–22.5 kHz) frequencies, the low-threshold point was located at the lateral side of the middle portion of the lower jaw. For lower frequencies, there was an additional low-threshold point next to the bulla-meatus complex. Based on these data, several frequency-specific paths of sound conduction to the auditory bulla are suggested: (i) through an area on the lateral surface of the lower jaw and further through the intra-jaw fat-body channel (for a wide frequency range); (ii) through an area on the ventro-lateral head surface and further through the medial opening of the lower jaw and intra-jaw fat-body channel (for a high-frequency range); and (iii) through an area on the lateral (near meatus) head surface and further through the lateral fat-body channel (for a low-frequency range).

Sylvain De Guise - One of the best experts on this subject based on the ideXlab platform.

  • organohalogen contaminants and metabolites in Beluga Whale delphinapterus leucas liver from two canadian populations
    Environmental Toxicology and Chemistry, 2006
    Co-Authors: Melissa A Mckinney, Daniel Martineau, Sylvain De Guise, Pierre Béland, Michel Lebeuf, Robert J Letcher
    Abstract:

    Contaminants described as organochlorines (OCs; e.g., polychlorinated biphenyls [PCBs]) are present in tissues of marine mammals, including Beluga Whales (Delphinapterus leucas), but the complexity of contaminant exposure often is not fully known. The PCBs, OC pesticides, polybrominated diphenyl ether (PBDE) flame retardants, methylsulfonyl (MeSO2)- and hydroxy (OH)-PCB metabolites, and OH-PBDEs and methoxylated (MeO)-PBDEs were determined in the liver of Beluga Whales from two Canadian populations: the St. Lawrence Estuary (SLB; n=6), and western Hudson Bay in the Canadian Arctic (CAB; n=11). The sigmaPCB, sigmaDDT, and sigmaPBDE concentrations were higher (p < 0.05) in SLB versus CAB. Of 18 detectable OH-PCBs in SLB (mainly 4-OH-CB107, 4-OH-CB112, and 4'-OH-CB120), only 4'-OH-CB120 was found in CAB. The sigmaOH-PCB concentrations were less than 0.2% of the sigmaPCBs in both populations but were higher (p < 0.05) in SLB (65 +/- 22 ng/g lipid wt) than in CAB (3.1 +/- 0.5 ng/g lipid wt). The sigmaMeSO2-PCB concentrations were higher in SLB (3801 +/- 1322 ng/g lipid wt) relative to CAB (77 +/- 23 ng/g lipid wt) and were 11 and 4%, respectively, of the sigmaPCB concentrations. Of the 15 OH-PBDEs, only two congeners were detectable, but not quantifiable (notably 2'-OH-BDE 68 and 6-OH-BDE 47), in animals from both populations. Of the 15 MeO-PBDEs, 4'-MeO-BDE 17 and 6-MeO-BDE 47 in the SLB (n=2) and 2'-MeO-BDE 68 and 6-MeO-BDE 47 in the CAB (n=2) had concentrations from 20 to 100 ng/g lipid weight. The OH-PBDEs and MeO-PBDEs most likely are of natural origin and accumulated in Beluga Whales, whereas the OH-PCBs and MeSO2-PCBs are metabolites derived from accumulated PCBs. Canadian Beluga Whale liver contains previously unidentified organohalogen contaminants and metabolites and, thus, a complexity of contaminant exposure that may be impacting the health of Canadian Beluga Whale populations.

  • biotransformation of polybrominated diphenyl ethers and polychlorinated biphenyls in Beluga Whale delphinapterus leucas and rat mammalian model using an in vitro hepatic microsomal assay
    Aquatic Toxicology, 2006
    Co-Authors: Melissa A Mckinney, Daniel Martineau, Sylvain De Guise, Pierre Béland, Augustine Arukwe, Robert J Letcher
    Abstract:

    Although polychlorinated biphenyls (PCBs) and polybrominated diphenyl ether (PBDE) flame retardants are important organic contaminants in the tissues of marine mammals, including those species from the Arctic, there is exceedingly little direct evidence on congener-specific biotransformation. We determined and compared the in vitro metabolism of environmentally relevant PCB (4,4'-di-CB15, 2,3',5-tri-CB26, 2,4,5-tri-CB31, 2,2',5,5'-tetra-CB52, 3,3',4,4'-tetra-CB77, 2,2',4,5,5'-penta-CB101, 2,3,3',4,4'-penta-CB105 and 2,3',4,4',5-penta-CB118), and PBDE (4,4'-di-BDE15, 2,4,4'-tri-BDE28, 2,2',4,4'-tetra-BDE47, 2,2',4,5'-tetra-BDE49, 2,2',4,4',5-penta-BDE99, 2,2',4,4',6-penta-BDE100, 2,2',4,4',5,5'-hexa-BDE153, 2,2',4,4',5,6'-hexa-BDE154 and 2,2',3,4,4',5',6-hepta-BDE183) congeners using hepatic microsomes of a Beluga Whale (Delphinapterus leucas) from the Arviat (western Hudson Bay) area of the Canadian Arctic. Ortho-meta bromine-unsubstituted BDE15, BDE28 and BDE47 were significantly metabolized (100%, 11% and 5% depleted, respectively) by Beluga, whereas control rat microsomes (from pooled male Wistar Han rats) metabolized BDE28, BDE49, BDE99 and BDE154 (13%, 44%, 11% and 17% depleted, respectively). CB15 and CB77 (putative CYP1A substrates) were more rapidly metabolized (100% and 93% depleted, respectively) by male Beluga than CB26 and CB31 (CYP1A/CYP2B-like) (25% and 29% depleted, respectively), which were more rapidly metabolized than CB52 (CYP2B-like) (13% depleted). Higher chlorinated CB101 and CB105 showed no depletion. Rat control microsomes metabolized CB15 to a lesser extent (32% depleted) than Beluga, but much more rapidly transformed CB52 (51% depleted, respectively). Within the 90 min in vitro assay time frame, the preference was towards metabolism of ortho-meta unsubstituted congeners (for both PCBs and PBDEs) in Beluga Whale, whereas for rat controls, meta-para unsubstituted congeners also substantially metabolized. For both Beluga Whale and rat, metabolic rates were inversely associated with the degree of halogenation. For the rapidly biotransformed CB15 and BDE15, water-soluble OH-metabolites were detected after incubation. These results indicate that CYP-mediated oxidative hepatic biotransformation is a metabolic pathway in the toxicokinetics of both PCB and PBDE congeners in Beluga Whales and in the rat model. This may suggest that the formation of potentially toxic oxidative PCB and PBDE products (metabolites), in addition to the parent pollutants, may be contributing to contaminant-related stress effects on the health of Beluga Whale.

  • Uterine adenocarcinoma with abdominal carcinomatosis in a Beluga Whale.
    Journal of Wildlife Diseases, 1998
    Co-Authors: Stéphane Lair, Sylvain De Guise, Daniel Martineau
    Abstract:

    A case of uterine adenocarcinoma is reported in a 26-yr-old, free-ranging Beluga Whale (Delphinapterus leucas) from the St. Lawrence estuary (Quebec, Canada). This neoplasm appeared as a segmental stenotic thickening of the left uterine horn composed of well differentiated, but disorganized and infiltrative, glandular structures surrounded by an extensive scirrhous stroma. Abdominal carcinomatosis was observed on the mesosalpinx and on the serosal aspect of the gastric compartments. This is the first report of a malignancy originating in the uterus of a cetacean.

  • phenotyping of Beluga Whale blood lymphocytes using monoclonal antibodies
    Developmental and Comparative Immunology, 1997
    Co-Authors: Sylvain De Guise, Daniel Martineau, Pierre Béland, Jacques Bernier, Michel Fournier
    Abstract:

    Abstract Widespread efforts are currently made to classify morphologically indistin-guishable lymphocyte subpopulations in several species. In order to increase the knowledge in cetacean immunology, cross-reactivity of antibodies against bovine, human, ovine and mouse cell surface proteins was tested on Beluga Whale ( Delphinapterus leucas ) peripheral blood lymphocytes using flow cytometry. Anti-MHC class I and II as well as anti-CD2 reacted with virtually all peripheral blood lymphocytes. Anti-TCR γδ and anti-CD4 reacted with respectively 31% and 30% of peripheral blood lymphocytes. B lymphocytes were identified by an antisurface IgM which was present on 6% of blood lymphocytes. Specificity of these antibodies was demonstrated by immunoprecipitation of Beluga proteins with similar molecular weight to that of other species. These results could be useful for further immunotoxicological evaluation of highly versus mildly contaminated populations of Belugas.

  • Effects of in vitro exposure of Beluga Whale splenocytes and thymocytes to heavy metals
    Environmental Toxicology and Chemistry, 1996
    Co-Authors: Jacques Bernier, Daniel Martineau, Sylvain De Guise, Michel Fournier, Pierre Béland
    Abstract:

    The effects of in vitro exposure of Beluga Whale splenocytes and thymocytes to different concentrations of mercury chloride (HgCl 2 ), cadmium chloride (CdCl 2 ), and lead chloride (PbCl 2 ) were evaluated. The cells were cultured for 66 h with either concanavalin A (Con-A), phytohemagglutinin-P, or without mitogen, after which percentage of cell death and proliferation were evaluated. Increased percentage of cell death was observed in Con-A-stimulated thymocytes cultured with HgCl 2 , while the viability of splenocytes was not affected by exposure to metals. Decreased splenocyte and thymocyte proliferation was observed with the highest concentration of HgCl 2 and CdCl 2 (10 -5 M), while lower concentrations of these metals (10 -6 and 10 -7 M) as well as all the different concentrations of PbCl 2 (10 -4 , 10 -5 , and 10 -6 M) did not significantly influence cell proliferation. Concentrations of metals that were found to affect the proliferation of Beluga lymphocytes are similar to those found in the liver of Beluga Whales from wild populations.

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  • adaptation in the auditory system of a Beluga Whale effect of adapting sound parameters
    Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2019
    Co-Authors: V V Popov, Alexander Ya. Supin, Dmitri I Nechaev, Evgeniya Sysueva
    Abstract:

    The effects of adapting sounds (pip trains or pure tones) on auditory evoked potentials (the rate following response, RFR) were investigated in a Beluga Whale. During RFR acquisition, adapting signals lasting 128 ms each were alternated with test signals lasting 16 ms each; the test signal levels varied randomly. Adapting signals were trains of cosine-enveloped tone pips or pure tones. Pip rate varied with the envelope cosine cycle maintained at 0.125 of pip intervals and the cosine rise-fall time maintained at 0.0625 of pip intervals. Adapting signals shifted the amplitude-level function upward compared to the baseline (no adapting signal) function. The higher the adapting signal level was, the bigger the shift in the amplitude-level function was. The slower the pips were in the adapting signal, the smaller the adaptation effect was. A train of pips with a 0.0625-ms rise-fall time and 125 dB SPL shifted the function by 35-40 dB, whereas a train of pips with a 1-ms rise-fall time or a pure tone with the same SPL shifted the function by approximately 15 dB. The difference between the "fast" and "slow" adapting signals is supposed to be associated with their abilities to stimulate the auditory system in odontocetes.

  • position of an acoustic window in a Beluga Whale computation based on auditory evoked potential latencies
    Journal of the Acoustical Society of America, 2019
    Co-Authors: V V Popov, Dmitry I. Nechaev, Ya A Supin, Alena Lemazina, Evgeniya Sysueva
    Abstract:

    In a Beluga Whale, the positions of sound receiving areas on the head surface were determined by comparing the acoustic delays from different sound source positions. For this investigation, auditory evoked potentials (AEPs) in response to short tone pips were recorded. Latencies of the first AEP wave that presumably reflected the activity of the auditory nerve were measured at different sound source azimuths. For AEPs of equal amplitudes, the difference in AEP latencies was attributed to the difference in the acoustic delays. These delay differences were used to compute the azimuths of sound receiving points. Measurements were conducted at frequencies from 22.5 to 90 kHz in half-octave steps. At all stimulus frequencies, the receiving points were located 24–38 cm caudal of the melon tip, which is near a proximal part of the lower jaw. Thus, the results indicated the latero-mandibular acoustic window. Possible causes for not finding a lateral or ventro-mandibular window are discussed.In a Beluga Whale, the positions of sound receiving areas on the head surface were determined by comparing the acoustic delays from different sound source positions. For this investigation, auditory evoked potentials (AEPs) in response to short tone pips were recorded. Latencies of the first AEP wave that presumably reflected the activity of the auditory nerve were measured at different sound source azimuths. For AEPs of equal amplitudes, the difference in AEP latencies was attributed to the difference in the acoustic delays. These delay differences were used to compute the azimuths of sound receiving points. Measurements were conducted at frequencies from 22.5 to 90 kHz in half-octave steps. At all stimulus frequencies, the receiving points were located 24–38 cm caudal of the melon tip, which is near a proximal part of the lower jaw. Thus, the results indicated the latero-mandibular acoustic window. Possible causes for not finding a lateral or ventro-mandibular window are discussed.

  • differential hearing sensitivity in the adaptive background in a Beluga Whale
    Journal of the Acoustical Society of America, 2018
    Co-Authors: V Popov, Alexander Ya. Supin, Dmitry I. Nechaev, Evgeniya Sysueva
    Abstract:

    The ability of the auditory system to maintain high differential sensitivity in the adaptive background was investigated in a Beluga Whale (Delphinapterus leucas). Adaptive background was a train of tone pips following one another at a rate of 1 kHz. Each pip consisted of eight carrier cycles of 64 kHz. Every 128 ms, the train of pips was interrupted for 16 ms and replaced with a test signal (16-ms series of the same tone pips as in the adaptive background, but of another level). The level of the test signals varied from -15 to + 20 dB relative the level of adaptive background. Evoked potentials (the rate following response, RFR) produced by the test signals were recorded. Increasing of adaptive level led to RFR thresholds growth. The 10-dB rising of adaptive signals intensity level led to 7.8 dB rising of test signal threshold. The response amplitude dependence on the test stimulus level was almost independent of the level of the adaptive background. Thus, the Beluga’s auditory system displayed high sensitivity to the change in acoustic signal level in the high-level background. [This study was supported by the Russian Foundation for Basic Research (Grant No. 18-04-00088).]The ability of the auditory system to maintain high differential sensitivity in the adaptive background was investigated in a Beluga Whale (Delphinapterus leucas). Adaptive background was a train of tone pips following one another at a rate of 1 kHz. Each pip consisted of eight carrier cycles of 64 kHz. Every 128 ms, the train of pips was interrupted for 16 ms and replaced with a test signal (16-ms series of the same tone pips as in the adaptive background, but of another level). The level of the test signals varied from -15 to + 20 dB relative the level of adaptive background. Evoked potentials (the rate following response, RFR) produced by the test signals were recorded. Increasing of adaptive level led to RFR thresholds growth. The 10-dB rising of adaptive signals intensity level led to 7.8 dB rising of test signal threshold. The response amplitude dependence on the test stimulus level was almost independent of the level of the adaptive background. Thus, the Beluga’s auditory system displayed high sens...

  • influence of the background noise on recognition of signals with a complex spectrum structure in the Beluga Whale delphinapterus leucas
    Doklady Biological Sciences, 2018
    Co-Authors: Evgeniya Sysueva, Dmitry I. Nechaev, V. V. Rozhnov, Ya A Supin, Mikhail B Tarakanov, V V Popov
    Abstract:

    The frequency resolving power of hearing (FRP) of the Beluga Whale Delphinapterus leucas was studied as dependent on influence of lasting low-intensity sounds (of the ultrasonic range from –20 to +10 dB). Testing of the spectrum ripple-phase reversal was used in conjunction with a noninvasive recording of auditory evoked potentials. FRP parameters were found to depend nonmonotonically on the intensity of the background noise. The resultant adaptation effects can be explained by the fact that, in response to the high-intensity signals, the auditory system sensitivity is reduced to the level optimal for analysis of these signals.

  • auditory evoked potentials in the auditory system of a Beluga Whale delphinapterus leucas to prolonged sound stimuli
    Journal of the Acoustical Society of America, 2016
    Co-Authors: V V Popov, Dmitry I. Nechaev, Evgeniya Sysueva, V V Rozhnov, Alexander Ya. Supin
    Abstract:

    The effects of prolonged (up to 1500 s) sound stimuli (tone pip trains) on evoked potentials (the rate following response, RFR) were investigated in a Beluga Whale. The stimuli (rhythmic tone pips) were of frequencies of 45, 64, and 90 kHz at levels from 20 to 60 dB above threshold. Two experimental protocols were used: short- and long-duration. For the short-duration protocol, the stimuli were 500-ms-long pip trains that repeated at a rate of 0.4 trains/s. For the long-duration protocol, the stimuli were continuous pip successions lasting up to 1500 s. The RFR amplitude gradually decreased by three to seven times from 10 ms to 1500 s of stimulation. Decrease of response amplitude during stimulation was approximately proportional to initial (at the start of stimulation) response amplitude. Therefore, even for low stimulus level (down to 20 dB above the baseline threshold) the response was never suppressed completely. The RFR amplitude decay that occurred during stimulation could be satisfactorily approximated by a combination of two exponents with time constants of 30-80 ms and 3.1-17.6 s. The role of adaptation in the described effects and the impact of noise on the acoustic orientation of odontocetes are discussed.